Improvements in the temperature-dependent properties of dielectric composites by utilizing MgO whiskers as the dielectric filler in an iPP matrix

• Dielectric and thermal properties of MgO whisker-filled composites were investigated.
• Dielectric loss of MgO whisker-filled composites were on the order of 10−4.
• Dielectric constant of MgO whisker-filled composites ranged from 2.4 to 3.6.
• Thermal conductivity, CTE and TCε of MgO whisker-filled composites were significantly improved.

MgO whiskers were synthesized and used as dielectric, thermally conductive fillers in isotactic polypropylene matrix composites. Composites with filler concentrations up to 30 vol% were prepared so as to study the composition dependence of dielectric and thermal properties. Composites containing cubic MgO particles were also prepared for comparison and the effects of anisotropic morphologies, the crystallinity and the particle size of the MgO filler on the properties of the composites were investigated. Dielectric constants increased with increasing filler concentrations but were almost independent of the type of filler. All composites exhibited low dielectric loss (tan δ) values on the order of 10−4. Both the filler crystallinity and particle size were found to be important with regard to obtaining low loss composites. The whisker-filled composites showed significant improvements in the temperature coefficient of dielectric constant (TCε) and thermal conductivity, due to the anisotropic whisker-shaped filler.

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